Novel insights into diminished cardiac reserve in non-obstructive hypertrophic cardiomyopathy from four-dimensional flow cardiac magnetic resonance component analysis.

AIMS: Hypertrophic cardiomyopathy (HCM) is characterized by hypercontractility and diastolic dysfunction, which alter blood flow haemodynamics and are linked with increased risk of adverse clinical events. Four-dimensional flow cardiac magnetic resonance (4D-flow CMR) enables comprehensive characterization of ventricular blood flow patterns. We characterized flow component changes in non-obstructive HCM and assessed their relationship with phenotypic severity and sudden cardiac death (SCD) risk. METHODS AND RESULTS: Fifty-one participants (37 non-obstructive HCM and 14 matched controls) underwent 4D-flow CMR. Left-ventricular (LV) end-diastolic volume was separated into four components: direct flow (blood transiting the ventricle within one cycle), retained inflow (blood entering the ventricle and retained for one cycle), delayed ejection flow (retained ventricular blood ejected during systole), and residual volume (ventricular blood retained for >two cycles). Flow component distribution and component end-diastolic kinetic energy/mL were estimated. HCM patients demonstrated greater direct flow proportions compared with controls (47.9 ± 9% vs. 39.4 ± 6%, P = 0.002), with reduction in other components. Direct flow proportions correlated with LV mass index (r = 0.40, P = 0.004), end-diastolic volume index (r = -0.40, P = 0.017), and SCD risk (r = 0.34, P = 0.039). In contrast to controls, in HCM, stroke volume decreased with increasing direct flow proportions, indicating diminished volumetric reserve. There was no difference in component end-diastolic kinetic energy/mL. CONCLUSION: Non-obstructive HCM possesses a distinctive flow component distribution pattern characterised by greater direct flow proportions, and direct flow-stroke volume uncoupling indicative of diminished cardiac reserve. The correlation of direct flow proportion with phenotypic severity and SCD risk highlight its potential as a novel and sensitive haemodynamic measure of cardiovascular risk in HCM.

Atrioventricular plane displacement correlates closely to circulatory dimensions but not to ejection fraction in normal young subjects.

AIMS: Mitral atrioventricular plane displacement (AVPD) provides information about left ventricular systolic function. M-mode of systolic annulus amplitude or tissue Doppler imaging of systolic annulus velocity are the current methods of evaluating AVPD. A correlation to ejection fraction (EF) has been demonstrated in patients with coronary artery disease and left ventricular dysfunction. Our aim was (i) to investigate the mitral AVPD of normal subjects with different physical work capacities and (ii) to further evaluate AVPD as an index of left ventricular systolic function. METHODS AND RESULTS: Twenty-eight healthy men mean age 28 years (20-39) were included: endurance trained (ET) (n=10), strength trained (ST) (n=9) and untrained (UT) (n=9). The systolic AVPD was recorded at four sites, septal, lateral, anterior and posterior, using M-mode. Left ventricular volumes were calculated according to Simpson's rule. Systolic AVPD was higher in endurance trained, 16.9 +/- 1.5 mm, as compared with both strength trained, 13 +/- 1.6 (P<0.001) and untrained, 14 +/- 1.6 (P<0.001). Left ventricular systolic AVPD correlated strongly with end-diastolic volume (r=0.82), stroke volume (r=0.80) and maximal oxygen consumption per body weight (r=0.72). The correlation between AVPD and EF was poor (r=0.22). CONCLUSION: In the subjects studied, with a range of normal cardiac dimensions, AVPD correlated to stroke volume, end-diastolic volume and maximal oxygen consumption per body weight, but not to EF. On theoretical grounds, it also seems reasonable that a dimension like AVPD is related to other cardiac dimensions and volumes, rather than to a fraction, like EF. AVPD is one parameter that is useful for evaluation of left ventricular systolic function but is not interchangeable with other measurements such as EF.